Patent GB-1016705-A (GB)
Title: Improvements in electric remote control apparatus
IPC: H02P1/08
Filed: 1962-08-09
Abstract: 1,016,705. Control of A.C. motors. WILFRID BROOKE, and HARRY HOWE. Aug. 9, 1962, No. 30525/62. Addition to 943,204. Heading H2J. [Also in Division H3] The application of a supply to a motor or other load through a plug-and-socket coupler is controlled by a series saturable reactor in the line circuit and shunt saturable reactor connected across the load on the dead side of the series reactor, the excitation circuit of the series reactor including linked contacts of the coupler so that when the coupler parts are separated, the excitation circuit of the series reactor is broken, the shunt reactor is consequentially excited, and substantially zero potential is obtained across the load contacts of the coupler. In one embodiment, Fig. 1, a single-phase supply L1, N is connected through a series saturable reactor C and contacts P1, P2 of a plug-and-socket coupler to a motor M1. The series reactor C may be of the type described in Specification 864,714 and derives its excitation from transformer windings GR1S, GR2S on a shunt saturable reactor GR, the excitation current being rectified at Hand the shunt reactor connected to dead-side terminals L1a, Na. The shunt reactor, on the other hand, derives its excitation from transformer windings 10, 11 on series reactor C by way of rectifier F. To start the motor, isolator switch V is closed and push-button K depressed so as to raise the impedance of the shunt reactor by terminating energization of its control windings GR1e, GR2e over contacts 30, 31, and to lower the impedance of the series reactor by connecting the D.C. output terminals of rectifiers H and F in series with the excitation winding 6, 9 over contacts 32, 33. When the button is released only rectifier H provides an output which maintains the series reactor energization over a circuit including a half-wave rectifier U. The motor is stopped by depressing button J which removes the energization from the series reactor and so enables an output to be obtained from its transformer winding 10, 11 which re-energizes the shunt reactor. The same condition is obtained by parting the coupler, since the removal of link W isolates the energizing circuit of the series reactor. A three-phase embodiment is described, Fig. 2 (not shown). Instead of transformer windings on the reactors, each reactor may be shunted by a transformer the secondary winding of which is connected to a respective rectifier F or H. A further embodiment, Fig. 4, comprises two groups of respectively opposed control windings GR1e, GR2e and GR1E, GR2E on the shunt reactor, and for on and off control of the motor by a switch K, only a single transformer E connected to the live side of the supply in association with a rectifier F need be provided. The excitation circuits alone are shown in Fig. 6, and with switch K open no excitation is applied to the series reactor control winding 6, 9, while equal and opposed currents flow in the two groups of control windings of the shunt reactor which are connected between terminals 34, 36 and 35, 36, respectively. Consequently the shunt reactor is unenergized and has a high impedance. When switch K is closed, the control windings of the series reactor are energized and the reactor impedance in the line substantially lowered. If the coupler is parted current flows only in the winding connected between terminals 34, 36 and consequently the series reactor has a high impedance and the shunt reactor a low impedance Push-button control may alternatively be used in which case a rectifier H is provided as shown in Figs. 6 and 7, which is energized from transformer windings GR1S, GR2S on the shunt reactor. The Fig. 4 circuit may be used in a three-phase arrangement, Fig. 5 (not shown).